1. Field of the Invention
This invention is related to the field of integrated circuits and, more particularly, to receiver circuits.
2. Description of the Related Art
Integrated circuits (ICs) generally include a core circuit that implements the various operations that the IC is designed to perform, a driver circuit that drives output signals from the core circuit to an external circuit, and a receiver circuit that receives input signals from the external circuit and provides the received signals to the core circuit. The driver and receiver circuitry buffer and isolate the core circuit from the external circuit, thus handling the larger loads, higher current flows, higher voltages, noise, etc. that are typically involved in external communications.
Some ICs are configured to receive “singled-ended” signals—that is, signals that are generated relative to a fixed reference voltage and transmitted over a single wire. Other ICs are configured to receive “differential” signals—that is, two complementary signals transmitted over two separate wires. Differential signaling is particularly well suited for use in high speed IC interfaces due to its improved power characteristics and noise immunity. In certain situations, however, it may be desirable for an IC to handle both single-ended and differential signals.
For example, the mobile double data rate 2 (mDDR2) memory interface (sometimes referred to as the low power DDR2 or LPDDR2 interface) permits single-ended data signaling with a differential clock and vice-versa. Configurations that use only differential or only single-ended signaling are also supported. Because a data signal is normally referenced with respect to a clock signal, an IC that receives these types of signals may have to account for timing differences between its differential and single-ended inputs.